The present invention relates generally to exhaust treatment for an internal combustion engine and more particularly, but not exclusively, to a method, system, and software utilized to determine when to stop providing reductant to a NOx adsorber while operating in a regeneration mode.
The Environmental Protection Agency (“EPA”) is working aggressively to reduce pollution from new, heavy-duty diesel trucks and buses by requiring them to meet tougher emission standards that will make new heavy-duty vehicles up to 95% cleaner than older vehicles. Emission filters in the exhaust gas systems of internal combustion engines are used to remove unburned soot particles from the exhaust gas and to convert harmful pollutants such as hydrocarbons (“HC”), carbon monoxide (“CO”), oxides of nitrogen (“NOx”), and oxides of sulfur (“SOx”) into harmless gases.
NOx storage catalyst units or adsorbers are used to purify exhaust gases of combustion engines. Generally speaking, these NOx storage catalyst units store or trap NOx while the engine is operating in a lean mode and remove NOx from the adsorber while the engine is operating in a rich mode. One of the necessary steps to regenerate a respective adsorber is to consume all of the oxygen on the surface of the catalyst (referred to as the oxygen storage component (“OSC”)). Before the oxygen on the surface of the adsorber can be consumed, the oxygen in the exhaust gas produced by the engine must first be consumed. Once this is accomplished, any additional reductant supplied will be used to consume the OSC on the surface of the adsorber and to regenerate the adsorber. Accordingly, there is a need for methods and systems for determining how much reductant should be supplied to an adsorber in order to properly regenerate the adsorber.